Nine cases of West Nile virus disease have been identified in humans so far this season
West Nile virus season usually lasts until October
The Health Department has identified a record-breaking 1,039 positive mosquito pools this season
September 13, 2021 — The Health Department today reminded all New Yorkers to continue to protect themselves against mosquitoes and West Nile virus. Mosquitoes are active in New York City from April through October. So far this season, 9 cases of West Nile virus disease have been identified in New Yorkers, 4 from the Bronx, 2 from Queens, 1 each from Brooklyn, Manhattan, and Staten Island. The amount of West Nile virus activity varies every year. To date, a record-breaking 1,039 West Nile virus-positive mosquito pools—mosquitoes gathered from the same trap site and tested together for the virus—have been identified. On average, the Health Department identifies 309 positive mosquito pools each season. Previously, 2018 was noted as a record with 1,024 positive pools for the entire mosquito season. This year’s warm, wet weather may be contributing to these higher counts.
“While the end of summer is around the corner, we want all New Yorkers to be aware that mosquitoes are still active and we’ve seen record numbers of activity this season,” said Health Commissioner Dr. Dave A. Chokshi. “When outdoors, make sure you wear insect repellent and remove standing water from your property. If you observe standing water not on your property, please report it to 311.”
The West Nile virus was first detected in New York City 22 years ago. Since 1999, the number of human cases has ranged from 3 to 47 annually. Of the 359 West Nile virus neuroinvasive disease cases reported through last year, 47 (13%) died due to their infection. New York City has over 40 species of mosquitoes, but West Nile virus is transmitted primarily by several Culex species, including Culex salinarius and Culex pipiens.
The Health Department has successfully helped control mosquito-borne diseases since the West Nile virus was first detected in NYC. The Department uses a comprehensive, integrated pest management approach to prevent and control mosquitoes which can transmit West Nile virus. This includes reducing standing water where mosquitoes can lay their eggs, applying larvicide in bodies of standing water that cannot be drained such as catch basins and marshland, and spraying pesticides to target adult mosquitoes where persistent West Nile virus activity is detected. The Agency’s data-driven approach relies on mosquito trapping and testing to determine where in the city to apply larvicides or other pesticides.
There are more than 50 permanent mosquito surveillance trap sites citywide, and the Health Department installs additional mosquito traps around affected areas to enhance mosquito surveillance. There are currently 106 surveillance traps in the five boroughs. The Health Department is treating catch basins with larvicide and has already conducted three aerial applications of larvicide in the marsh areas of Staten Island, Brooklyn, Queens, and the Bronx. The agency has conducted 21 spray operations to control adult mosquitoes so far this season.
West Nile virus infection can cause a mild or moderate febrile illness; and most (80%) of those infected have no symptoms at all. In some people, particularly those 50 and older or who have weakened immune systems, West Nile virus can cause a serious and potentially fatal infection of the brain and spinal cord. The most common symptoms are headache, fever, muscle aches, and extreme fatigue. Symptoms of more severe illness can also include changes in mental status and muscle weakness requiring hospitalization. Most patients who are infected with WNV will go on to fully recover from their illness. However, some continue to have problems months after infection. If a person has symptoms of West Nile virus, they should contact or see their doctor.
Most New Yorkers diagnosed with West Nile virus report they did not use repellent or take other precautions to prevent a mosquito bite. Remember to obtain repellent for yourself, and also offer to get it for your older neighbors or relatives. For information about which repellent is best for you, visit the EPA site to search by product and duration of effectiveness.
Every year, as a part of normal outreach, the Health Department also conducts 80 to 90 presentations to educate communities about mosquito-borne illnesses. You can request community presentations on West Nile virus and other health topics.
For more information about West Nile virus, or to report standing water, visit nyc.gov/health/wnv or call 311.
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